Myopia, or near-sightedness, affects a substantial proportion of the world's population, especially in some Asian countries. Myopia is typically associated with an abnormal elongation of a person's eyeball. The elongated eyeball results in the retina being located out of the “normal” focal plane such that distant objects are focused in front of the retina rather than on the plane of the retina. The elongated eyeball associated with more severe myopia can also be associated with retinal detachment, glaucomatous damage and degenerative myopic retinopathy.
Efforts for reducing the progression of myopia have been attempted and include using multifocal spectacle or contact lenses, using lenses which affect optical aberrations, reshaping the cornea, and using pharmacological agents. Some ophthalmic lenses have been described for reducing progression of myopia that include a vision correction area that provides clear vision at near and distant viewing distances and a myopic defocus area that provides a defocused image at near and distant viewing distances. Difficulties associated with some of the proposed attempts at reducing myopia progression include pharmaceutical side effects, discomfort, compromised vision, or combinations thereof.
Contact lenses which provide both a focused retinal image during distance and near viewing, and a myopic defocused retinal image simultaneously to the eye(s) of a contact lens wearer during both near and distance viewing have been previously described for preventing or slowing the progression of myopia, for example, in U.S. Patent Application Publication No. US 20080062380, CONTACT LENSES AND METHODS FOR PREVENTION OF MYOPIA PROGRESSION, and in U.S. Patent Application Publication No. US 20080218687, CONTACT LENSES AND METHOD, each of which is hereby incorporated by reference in its entirety. These lenses have been found to be effective in correcting myopia and slowing its progression in many contact lens wearers, and can also be used to correct cases of hyperopia and to slow its progression.